This study aims to make clear the effect fluctuations of surrounding air velocity and its temperature have on the evaporation rate of fine drops. The evaporation rates of drops in an air flow with variation of temperature, amplitude and frequency of air velocity are measured. The results show that the critical evaporation rate coefficient, keo, decreases with the decrease of drop size less than 130 µm, though previous work has shown that keo remains constant regardless of drop diameter. The critical evaporation coefficient of a drop in fluctuating air flow increases with increasing amplitude and frequency because the mean value of instantaneous relative velocities becomes larger with amplitude and frequency under the same relative time mean velocity. A modified critical evaporation rate coefficient keo', which is calculated by substituting the instantaneous relative velocity, is proposed and it is shown that the evaporation rate of fine drops in fluctuating air flow can be expressed by keo'.